RTV high heat sealant for water pump fittings?

If it touches water and has threads, use thread sealant.

If it touches water and doesn't have threads, use a gasket.

I only use rtv where no gasket is used and rtv is specifically called out, as in diff covers, late model oil pans, etc.

If I do use rtv where there is an issue with sealing such as a pitted surface, I use the 'ultra' stuff. It didn't pull off like the cheap stuff.

That all said, any port in a storm. I've seen very sketchy uses of rtv that were quite successful.